基于孔隙介质模型的断层同震弱化与强化分析

One aspect of earthquake complexity is recognized to be related to pore fluid, and changes in pore fluid pressure can alter effective stress and thus change fault behavior. To analyze the effects of coseismic pore pressure change on rupture propagation, we perform simulations of the spontaneous rupture process based on a poroelasticity model in this paper. Biot′s theory of dynamic poroelasticity is used to model the fluid saturated rocks, and a hydraulic resistance model is utilized to depict the permeability of the fault zone core. Results indicate that coseismic pore pressure change can promote or hinder the propagation of rupture to some extent. If the fault zone core is impermeable, the compressive deformation of the near fault zone induces positive pore pressure change. This pore pressure buildup decreases frictional strength on the slipping surface, facilitating the propagation of rupture and weakening the fault. Meanwhile, the shear stress peak preceding rupture front increases obviously. The increase in shear stress peak and the decrease in frictional strength at rupture front make it easier to trigger a supershear rupture. In contrast, rupture induces negative pore pressure change in the region where the fault zone suffers extensional deformation. This negative pore pressure increases frictional strength and strengthenes the fault by hindering rupture propagating. This strengthening effect suppresses the occurrence of supershear rupture even if the initial shear stress is high.